.parent {
  width: 500px;
  background-color: antiquewhite;
  padding: 12px;
}

.child {
  width: 100%;
  padding: 12px;
  background-color: aquamarine;
}

.grand {
  width: 100%;
  padding: 12px;
  background-color: gray;
  margin-top: 12px;
}
